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Proceedings Paper

Extraction of fast neuronal changes from multichannel functional near-infrared spectroscopy signals using independent component analysis
Author(s): Geert Morren; Martin Wolf; Philippe Lemmerling; Ursula Wolf; Jee Hyun Choi; Enrico Gratton; Lieven De Lathauwer; Sabine Van Huffel
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Paper Abstract

Fast changes in the range of milliseconds in the optical properties of cerebral tissue, which are associated with brain activity, can be detected using non-invasive near-infrared spectroscopy (NIRS). These changes in light scattering are due to an alteration in the refractive index at neuronal membranes. The aim of this study was to develop highly sensitive data analysis algorithms to detect this fast signal, which is small compared to other physiological signals. A frequency-domain tissue oximeter, whose laser diodes were modulated at 110MHz was used. The amplitude, mean intensity and phase of the modulated optical signal was measured at 96Hz sample rate. The probe consisting of 4 crossed source detector pairs was placed above the motor cortex, contralateral to the hand performing a tapping exercise consisting of alternating rest- and tapping periods of 20s each. The tapping frequency, which was set to 3.55Hz or 2.5 times the heart rate of the subject to avoid the influence of harmonics on the signal, could not be observed in any of the individual signals measured by the detectors. An adaptive filter was used to remove the arterial pulsatility from the optical signals. Independent Component Analysis allowed to separate signal components in which the tapping frequency was clearly visible.

Paper Details

Date Published: 5 June 2002
PDF: 9 pages
Proc. SPIE 4623, Functional Monitoring and Drug-Tissue Interaction, (5 June 2002); doi: 10.1117/12.469474
Show Author Affiliations
Geert Morren, Katholieke Univ. Leuven (Belgium)
Martin Wolf, Univ. of Illinois/Urbana-Champaign (United States)
Philippe Lemmerling, Katholieke Univ. Leuven (Belgium)
Ursula Wolf, Univ. of Illinois/Urbana-Champaign (United States)
Jee Hyun Choi, Univ. of Illinois/Urbana-Champaign (United States)
Enrico Gratton, Univ. of Illinois/Urbana-Champaign (United States)
Lieven De Lathauwer, Katholieke Univ. Leuven (Belgium)
Sabine Van Huffel, Katholieke Univ. Leuven (Belgium)

Published in SPIE Proceedings Vol. 4623:
Functional Monitoring and Drug-Tissue Interaction
Manfred D. Kessler; Gerhard J. Mueller, Editor(s)

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